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Bad function arity and warning: function hello_world/0 is unused

I just started learning Erlang so I coded this as new.erl:

-module(new).
-export([hello_world]/0).
 hello_world()->io:fwrite("Hello\n").

So the function name is hello_world and it holds Hello as string.

But whenever I want to run this, I get this result:

new.erl:2: bad function arity
new.erl:3: Warning: function hello_world/0 is unused
error

So how to solve this problem, what's going wrong here ?

Solution

  • You wrote:

     -export( [ hello_world ]/0 )

    It should be:

     -export( [ hello_world/0 ] ).

    export requires a list, where each element in the list is the function name followed by a slash followed by the arity of the function. A list does not have an arity, which is what you wrote.

    Note that when you are just writing test code, it is easier to use:

    -compile(export_all).

    which will export all functions defined in your module.